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Bug Detective Roots Around Cornfields at Night

Jonathan G. Lundgren is a bug detective who hangs around cornfields late at night looking for "muggers." He finds them by shining an invisible light on them, red light only he can see.

Lundgren, an entomologist at the ARS North Central Agricultural Research Laboratory in Brookings, S.D., even does DNA tests on the muggers to link them to their victims.

But, unlike a crime detective, Lundgren likes the muggers and wants them to attack more, not less. Thats because these muggers are creepy-crawly hunters, including ground beetles, rove beetles, spiders, crickets, and daddy-longlegs. Their victims are other underground creatures, hopefully corn rootworms.

Corn rootworms are the real bad guys. They kill corn plants by eating their roots.

But with all these hunters crawling around in the first three inches of topsoil, all near corn roots, dont things get too crowded for good hunting?

Thats what Lundgren wondered, and so he is studying the bugs at night. Lundgren's research showed that the bugs don't all hunt at the same time.

Lundgren found that one common carabid beetle, Poecilus chalcites, prefers day work, while another common carabid, Cyclotrachelus alternans, works the night shift, 10 p.m. to 3 a.m. Wolf spiders search for rootworms during the night, while some other spiders hunt during the day.

Lundgren has noticed that there is more daytime activity in fields where grass or other plants are growing, compared to fields left bare after harvest.

"This could explain why cover crops planted after harvest reduce the numbers of corn rootworms and other pests, said Lundgren. They attract day and night hunters.

Lundgren has two ways to spy on hunter bugs. One is to place pinned corn rootworms as sentinels. He comes back later to see which have been attacked and which hunters are hanging around, waiting to attack. His second method is to collect predators in a timed trap. He analyzes trapped hunters for corn rootworm DNA. This tells him both the time that the predators are hunting, and the amount of rootworms eaten.